Photosensitizing dye effective for infra-red radiation



i STT'ES PATENT OFFICE.

ELLIOT Q. ADAMS, 0F BERKELEY, CALIFORNIA, AND HERBERT L. HALLER, 0F

CINCINNATI, OHIO.

PEOTUSEN'SITIZING DYE EFFECTIVE FOR INFRA-RED RADIATION.

No Drawing.

Specification of Letters Patent.

Patented Apr. 12, 1921.

Application filed July 17, 1920. Serial No. 307,114.

To all whom it may concern:

Be it known that we, ELLIOT Q. ADAMS and HERBERT L. HALLER, citizens ofthe United States of America, and employees of the. Department ofAgriculture, residing in the city of Berkeley, county of Alameda, Stateof California, and in the city of Cincinnati, county of Hamilton, Stateof Ohio, respectively, whose post office address. is Department ofAgriculture, Washington, D Q, have invented new and usefulPhotosensitizing Dyes Effective for Infra-Red Radiation, of which thefollowing is a specification.

Dyes of this type are known to be substituted ammonium salts, thesensitizing action being due to the positive ammonium radical. Hence,the nature of the negative radical will be of influence only in so faras it affects adversely the solubility of the compound or possessesdeleterious action of its own. It will therefore be possible to use anyquaternary compounds satisfactory in these respects.

This application is made under the act of. March 3, 1883, chapter 143(22 Stat. L., 625), and the invention herein descrlbed and claimed maybe used by the Government of the United States or any of its officers oremployees in the prosecution of work for the Government, and any personin the United States, without payment to; us of any royalty thereon.

It is known that a mixture of the quaternary halids (or other additionproducts) of quinolin and quinaldin,'or', more generally, of anoz-methylated and a y-unsubstituted quinolin base,yields withstrong-bases in alcohol solution a 'dye of the iso-cyanin type; while amixture of the quaternary halids (or other addition products) ofquinolin and lepidin,.or, more generally, of a y-methylated and a y-unsubstituted quinolin base,-yields with strong bases in alcoholsolution a dye of the cyanin type. By

oz-methylated quinolin bases are meant de rivatives of quinolin, orrelated bases, having a methyl group adjacent to the nitrogen of theheterocyclic ring, and by -unsubstituted quinolin bases andy-methylatedquinolin bases are ,meant derivatives of quinolin, and related bases,having, respectlvely, a

' hydrogen and a methyl group diametrically opposite the nitrogen of 1the heterocyclic ring. By strong bases are meant sodium and potassiumhydroxid, silver oxid, and the methylates and ethylates of sodium andpotassium. I

We have found that the quaternary halids or other addition products ofsu'iiiciently pure lepidin, or other -methylated quinolin bases, yieldwhen treated with strong bases under suitable conditions dyes effectivefor infrared radiation, whose sensitization maximum lies farther intothe infra-red than that of the dicyanins. Low concentration of reagents,high radical weight of the alkyl group attached to the nitrogen of theheterocyclic ring, and the presence of formaldehyde or chloroform favorthis type of condensation. By higher alkyl roup is meant an alkyl groupheavier than t e ethyl group; by higher quaternary additionprodnets-quaternary addition products 0011- taming such higher alkylgroups.

The characteristic absorption maximum of this class of dyes is in theneighborhood of 70005, their sensitization maximum at approximately7400A The following examples will serve to illustrate the preferredprocedure. The invention, however, is not confined to these exam ples.The parts are by weight.

Example 1: 1.5 parts of epidin ethiodid are dissolved in 320 parts ofabsolute methyl alcohol, and a solution of sodium mthylate prepared bydissolving 0.058 part of metallic sodium in 80 parts of absolute methylalcohol is added. After standing 100 hours the solution is poured into1000 parts of distilled water, the solution extracted with carbon'tetrachlorid to remove by-products, the dye extracted from v thesolution with chloroform, and the extract washed with water, dried overanhydrous sodium sulfate and evaporated to a small volume. Theconcentrated solution is poured into1'20 parts of anhydrous ethyl etherand the bluish black yield is small.

Example 2: 1.57 parts of lepidin isoproyl iodid are dissolved in16Iparts of absoute methyl alcohol and heated to-boiling.-

A solution of sodium methylajte prepared by dissolving 0.058 part ofmetallicsodium in 4 parts of absolute methyl alcohol is;

added. After standing for some time the precipitate filtered ofi. The

solution is concentrated to one-fourth of its original volume and pouredinto 150' parts of absolute ether. The precipitate is removed byfiltration, washed successively with absolute ether, water, and absoluteether, and, after drying, dissolved in absolute methyl alcohol, and thesolvent removed by evaporation at room temperature. The yield isapproximately 0.35 part of a purplish-black powder.

Example 3: 6 parts of lepidin ethiodid are dissolved in 80 parts of 95.per cent. ethyl alcohol and heated to boiling under a reflux condenser.After the air in the flask has been expelled a mixture of 1 part pf 40per cent. formaldehyde solution and a solution of sodium ethylate,prepared by dissolving 0.23 part of metallic'sddium in 16 parts ofabsolute ethyl alcohol, is added gradually. The boiling is continued tenminutes, the flask stoppered and allowed to cool slowly. After 24 hoursthe dye is filtered off, washed with ice-cold ethyl alcohol and finallyether. The yield is approximately 0.4 part'of a purplish-black powderwith a few crystals large enough to'give distinct reflections.

Example 4: 1.5 parts of lepidin methiodid are dissolved in 28 parts of95 per cent. ethyl alcohol, the solution heated to boiling under areflux condenser to expel air, and 22.5 parts of chloroform added. Asolution of sodium ethylate, prepared by dissolving 0.115 part ofmetallic sodium in 8 parts of absolute ethyl alcohol, is then rungradually directly into the boiling solution, and the boiling'continuedten minutes after the addition is complete. The flask is stoppered whilehot and allowed to cool slowly. After 24 hours the dye is filtered off,washed successively with ice-cold 95 per cent. ethyl alcohol, absoluteether, water, mixtures of alcohol and ether, and finally absolute ether.The yield is approximately 0.05 part of microscopic crystals showingboth green and copper-colored metallic reflection.

Example 5 4.5 parts of p-tolulepidin are dissolved in 32 arts of 95 percent. ethyl alcohol, and a so ution of 2.5 parts of silver nitrate in 48parts of 95 per cent. ethyl alcohol added, with stirring. Theprecipitated silver iodid is filtered off, the solution concentrated tothree-fifths of its original volume and heated under arefiux condenserto expel air. A solution of sodium ethylate prepared by dissolving 0.23part of metallic sodium in 16 parts of absolute ethyl alcohol and 0.75part of a 40 per cent. aqueous solution of formaldehyde are mixed andslowly added to the boiling solution. The boiling is continued tenminutes after the complete addition of the sodium ethylateformaldehydemixture, the flask stoppered while hot and allowed to cool very slowly.After 24 hours the dye is filtered off, washedsucoessivel with ice-cold90 per cent. ethyl alcohol, et er, water, a mixture of absolute etherand alcohol, and finally absolute ether. The yield is approximately 0.25part of a crystalline powder with a yellow green metallic luster.

Having now fully described our invention, what we claim and desire toprotect by Letters Patent is:

1. Dyes effective for infrared photographic sensitization produced bythe action of strong bases uponthe higher alkyl halids of lepidin.

2. Dyes effective for infra red photographic sensitization produced bythe action of strong bases on the higher quaternary addition products ofY-methylated quinolin bases.

3. Dyes effective for infra-red photographic sensitization produced bythe action of strong bases in the presence of formaldehyde on thequaternary addition products of y-methylated uinolin bases.

4. Dyes effective for infra-red photographic sensitization produced bythe action of strong bases in the presence ofchloroform on thequaternary addition products of r-methylated quinolin bases.

5. The process of producing photographic sensitizing dyes e'fiective forinfra-red radiation by the action of sodium ethylate and formaldeh de inalcohol solution on the alkyl halids o lepidin.

6. The process of producing photographic sensitizing dyes effective forinfra-red radiation by the action of strong bases and formaldehyde onthe quaternary addition products of -methylated quinolin bases.

7. The process of producing photographic sensitizing dyes effective forinfra-red radiation by the action of strong bases and chloroform on thequaternary addition products of y-methylated quinolin bases.

8. The process of producing photographic sensitizing dyes effective forinfra-red radiation by the action of strong bases on the higherquaternary addition products of ymethylated quinolin bases.

In testimony whereof, we afiix our signaturesin the presence of twosubscribing witnesses."

ELLIOT Q. ADAMS. HERBERT L. HALLER.

